Q & A

Q & A; Birth Pangs

By C. CLAIBORNE RAY

Published: January 28, 2003

Q. Why do humans, unlike virtually all other mammals, experience so much pain in giving birth?

A. The standard explanation is that the evolutionary growth of the human cranium outstripped the size and configuration of the human birth canal, especially the passage through the pelvis (which had to remain narrow so that people could walk on two feet), creating a uniquely difficult job. But recent research suggests that the matter is not so simple.

Studies of nonhuman primates have found that their offspring may face an even more tortuous route on the way out and that the relative difference between head size and pelvic diameter is larger in some nonhuman species.

One researcher, Dr. Wenda Trevathan, an evolutionary anthropologist at New Mexico State University, even argues that the pain and anxiety surrounding human birth serve a lifesaving purpose.

Since women know that giving birth is a really hard job, she suggests, they recruit help in giving birth, unlike virtually all other mammals. This often saves both woman and child, she says, because the position in which anatomy dictates that the baby emerge, downward and facing backward, makes it impractical for the woman to extricate the newborn and make sure it is free of the umbilical cord and mucus.

She also suggested that assisted childbirth coincided with the advent of bipedalism and long predated the cranial growth surge. C. CLAIBORNE RAY